Magnet Mag
Magnet Mag
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 New K 30 K30 Magnetic Mag Mount CB Radio Antenna NIB  US $31.95
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 NEW Maxrad NMO Magnetic Mount ALL Black Magnet Mag NIB US $28.00
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 New K 30 K30 Magnetic Mag Mount CB Ham Radio Antenna US $20.00
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 Wilson 1000 Magnet Black Mag Mount CB Radio Antenna US $79.99
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 K 40 Magnet Mount CB Radio Antenna K40 Mag Mount NEW US $82.99
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 K 30 Magnetic Mount CB Radio Antenna K30 Mag Mount NEW US $32.49
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 Wilson 2 Meter Magnet Mag Mount CB Radio Antenna Black US $52.99
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 5 INCH NMO CHROME NMO MAG MAGNET MOUNT pl 259 US $19.99
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 CHROME NMO MAG MAGNET MOUNT pl 259 35 INCH BR 316 US $16.99
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 New UHF ALL Black Mag Magnetic Mount Antenna w 3 magnet NIB US $38.00
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 Hustler MRM Magnet Mag Mount Scanner Antenna NEW US $29.95
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 CHROME UHF MAG MAGNET MOUNT pl 259 35 INCH TRAM BROWNING 3239 US $16.99
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| The Ham Radio Blog |
All About Rare Earth Magnets
Rare earth magnets are a special type of magnet, first manufactured in the 1970s. They are made from rare earth metals, which are a group of seventeen elements found in the periodic table. These include scandium and yttrium, and despite the name, they are actually found in relative abundance in the earth's crust. Rare earth magnets have the distinction of being the most powerful type of permanent magnet. They are much stronger than the more well known ferrite or alnico magnets. Rare earth magnets can produce a magnetic field that is stronger than 1.4 teslas, while the other types make fields of 1 tesla or less. Rare earth magnets are powerful chiefly because they have what is known as high magnetic anisotropy. High anisotropy means that the crystals within the rare earth metals are easy to magnetize in a specific direction, but hard to magnetize in other directions. These magnets also have high coercivity, which means that they have a strong resistance to losing their magnetic properties. However, they are also very brittle and rust easily. Usually they are covered with some kind of coating or plating to keep them from getting chipped or broken. In addition, if you want to buy rare earth magnets, you need to be aware that they are considerably more expensive than other types of magnets.
The two types of rare earth magnets are samarium-cobalt and neodymium. The sarium-cobalt type was the first to be invented in the 1970s, and is more brittle and weaker than the neodymium type, which was invented about a decade later. The samarium-cobalt type is also more expensive. However, it has the advantage of a higher Curie temperature, which means that it can be used at higher temperatures without losing its magnetism. The neodymium type, made of neodymium, boron, and iron, are much more widely used.
Rare earth magnets have not normally been used as refrigerator magnets or in other ways that consumers typically use alnico and ferrite magnets, because of their cost. They are primarily used industrially, as parts of appliances. One of the most common industrial uses of rare earth magnets is in most computer hard drives. They are also found in speakers and headphones, cordless tools, and mag-lev trains. As prices have come down over the years, more and more consumers buy rare earth magnets for household uses such as finding nails under flooring, erasing video tapes, attaching tarps to cars, or re-magnetizing old alnico magnets that have become demagnetized.
The best way to buy rare earth magnets is to go online and do some patient searching. Use a search engine such as Bing or Google, and start with a search term like "buy magnets" or "magnet prices". Be sure to look at a large number of websites before making any decisions. Verify that the store has a reasonable return policy, and that there are no hidden costs such as shipping and handling costs.
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NIB magnets Magnetic Field?
Hi there !
i am a building right now a generator based on scrap NIB magnets found in Hard drives and wanted to be able to calculate the Magnetic Field 'B' that emanates from them in order to find out the rate of flux change in the coil above them.
for this i need
a - to know what grade are these magnets usualy are ?
b - how can you calculate B based on the volume and shape of the magnet ?
c - how does B behave outside of the magnet in relation to the distance from it (i know that NIB mag. have about 1T on the surface, right ?)
d - how can you calculate the field B in an air core coil and in an iron core coil ?
if anyone can help me understand the equations i'd be most gratefull.
thanks !!!
You are not asking a simple question. There are so many variables that it would be easier to build a generator, test it, and change something if you don't like the results.
In order to solve the problem you would need to model it in a magnetic FEA program (five figure price tag). The problem is solved by working with H throughout the circuit and then computing B from B = mu*H in the various parts. Be aware the mu changes dramatically in ferromagnetic materials as you begin to approach saturation.
This might help:
http://www.arnoldmagnetics.com/mtc/pdf/TN_9802.pdf
Sorry. I wish I could be more helpful
